Machining with small diameter tools, for example less than 8 mm diameter, requires high speed machining capability in the range of 20,000, 30,000, 50,000 and in some cases over 100,000 RPM. Small diameter tools are typically used for applications requiring small geometries as well as general purposes applications in the semi finish and finish processes of most manufactured parts. Machining with small diameter tools is also referred to as micro machining.
In micro machining, the required rotation speeds are higher while the power requirements are relatively low compared to non-micro machining. High speed machining for semi finish and finish processes requires effective cutting tool and cutting location cooling as well as effective chip removal.
Computerized machining centers typically include an Automatic Tool Changer (ATC), such that multiple machining operations can be performed on the same part, i.e. using different tools that are changed automatically by the ATC, without removing the part. This capability provides significant cost savings, reduces manpower requirements and improves manufacturing quality and yield.
Most machining centers use electrical motor driven spindles to rotate the machining tools. General purpose machining spindles rotate at speeds of a few thousands RPM. Spindles capable of higher RPM are expensive and often used on dedicated equipment. The result is that many smaller diameter cutting tools are used at suboptimal machining conditions or that parts requiring semi finishing and or finishing operations have to be moved to other machine centers, with higher speed spindles. Both options are problematic.
Present solutions such as speed increasers and other non-electric spindles are often susceptible to problems.